1. Field of the Invention
The present invention relates to an indwelling needle assembly used for introducing a catheter into a vascular system of a patient at a time of infusion.
2. Description of the Related Art
Catheters are used to infuse various medicinal fluids into vascular systems. To introduce such a catheter into a vascular system of a patient, a needle assembly with a needle fitted in the catheter is frequently used. After sticking the needle into the vascular system, the needle may be extracted but the catheter is left indwelled in the vascular system. When the needle is extracted, the needle must be safely covered so as to prevent accidental sticking. Some catheters are provided with telescopically extensible sleeves for covering the needles. However, extension of the sleeves by hands in itself may give rise to a risk of accidental sticking. An automatic extension mechanism may need a complex structure.